Contraceptive oral pills help in birth control by
(a) killing the sperms in uterus
(b) preventing implantation
(c) preventing ovulation
(d) both (b) and (c).
Contraceptive oral pills supplies a steady level of both progestogen and/or estrogen every day. This steady supply of hormone helps stopping ovulation. So, when birth control stops ovulation, an egg is not released from the ovary.